Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Prepublication Copy
GRAND CHALLENGE 2:
Curb Climate Change
and Adapt to Its
Impacts
It is now more certain than ever that humans are changing
Earthâs climate.97 The burning of fossil fuels for electricity generation,
transportation, heating, cooling, and other energy uses has raised the
concentration of global atmospheric carbon dioxide (CO2) to more than
400 parts per million (ppm)âa level that last occurred about 3 million years ago
when both global average temperature and sea level were significantly higher
than today.98 At the same time, the production of fossil fuels and agricultural and
industrial processes also have emitted large amounts of methane and nitrous oxide,
both powerful greenhouse gases, into the atmosphere.
The heat trapped by the sharp rise in greenhouse gases has increased Earthâs global
average surface temperature by about 1.8Â°F (1.0Â°C) over the past 115 years, and
at an increased rate since the mid-1970s (see Figure 2-1).99 This warming has been
accompanied by rising sea levels, shrinking Arctic sea ice, reduced snow pack,
and other climatic changes. Many urban areas across the globe have witnessed a
significant increase in the number of heat waves. More rain is falling during the
heaviest rainfall events, causing flooding and further stressing low-lying coastal
26â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
FIGURE 2-1.â Earthâs global average surface temperature has risen about 1.8Â°F (1.0Â°C) over the past 115 years, with
much of that increase occurring since the mid-1970s. The temperature changes (anomalies) are relative to the global
average surface temperature of 1951â1980.
zones already vulnerable to storm surges and other causes of temporary coastal
flooding, along with sea-level rise.100 In other areas, prolonged dry periods and
droughts are increasing the risk of destructive wildfires and water shortages.
If greenhouse gas emissions continue to rise in the 21st century, Earth is expected to
warm by an additional 4.7Â°F to 8.6Â°F (2.6Â°C to 4.8Â°C) by 2100 (relative to 1986-
2005).101 The greater the warming, the greater the impacts will be. In the United
States, each degree of warming (Celsius) is projected to result in a 3 to 10 percent
increase in the amount of rainfall during the heaviest rain events, a 5 to 15 percent
reduction in the yields of crops as currently grown, and a 200 to 400 percent
increase in the area burned by wildfire in western states.102 Similar types of changes
are expected in many other parts of the world, which could be most devastating to
low-income countries that do not have the resources to respond or adapt.103
Warming of about 5.4Â°F (3Â°C) or more could push Earth past several âtipping points.â
For example, this amount of warming could melt the Greenland ice sheet, which would
raise global average sea level an additional 20 feet (6 meters).104 It could also accelerate
the thawing of permafrost, which would accelerate the release of CO2 and methane
stored in frozen soil, exacerbating warming.105 While projections such as these are
useful in planning for the changes ahead, it is also important to recognize that a great
deal remains unknown, particularly when it comes to the complex feedbacks among
human activities, ecosystems, and the atmosphere.
For decades, scientists have led the efforts to understand and predict climate change
effects, but engineers are now recognizing that their efforts are needed to help develop
and implement solutions. Conceptually, climate solutions are divided into two areas of
focus: mitigation and adaptation. Mitigation refers to efforts to reduce the magnitude or
rate of climate change by reducing emissions of carbon dioxide and other greenhouse
gases or removing them from the atmosphere. Adaptation refers to solutions that
avoid or lessen the impacts of climate change on people, ecosystems, resources, and
Curb Climate Change and Adapt to Its Impactsâ |â 27

Prepublication Copy
infrastructure. Environmental engineers have an opportunity to be leaders in developing
technologies and systems that provide solutions on both of these fronts. Given that future
climate changes likely hold surprises, it will be important to remain nimble, incorporate
new knowledge, and work to address uncertainty as environmental engineers develop,
test, and implement solutions.
Reducing the Rate and Magnitude of Climate Change
A sharp reduction in emissions of greenhouse gases to the atmosphere is needed to
slow climate change and prevent some of the most severe impacts. For the past few
decades, international climate talks have focused on establishing goals to minimize
the planetâs warming, with the most recent goals set at limiting future warming to
3.6Â°F (2Â°C) above preindustrial levels. The 2016 Paris Agreement set an aspirational
target of limiting warming to 2.7Â°F (1.5Â°C). Since the planet already has warmed
about 1.8Â°F (1Â°C), scientists have calculated that, in order to stay within the 3.6Â°F
(2Â°C) limit, atmospheric CO2 concentrations must not rise beyond 450 ppm, which
in turn requires 40 to 70 percent reductions in global anthropogenic greenhouse
gas emission by 2050 compared to 2010, and emissions levels near zero or below
in 2100.106
A special report issued in 2018 by the Intergovernmental Panel on Climate
Change urged world leaders to work toward limiting warming to 2.7Â°F (1.5Â°C) to
avoid the severe impacts on weather extremes, ecosystems, human health, and
infrastructure that are expected to occur at 3.6Â°F (2Â°C) warming.107 Meeting that
tougher goal will require global emissions to be reduced by about 45 percent
from 2010 levels by 2030, reaching net zero emissions by 2050. Meeting those
emmissions targets will require dramatic reductions in global CO2 emissions
combined with the active removal of CO2.108
Greenhouse gas emissions are driven by
the use of energy for electricity generation,
transportation, industry uses, commercial
and residential needs, and agriculture.
Figure 2-2 shows the U.S. breakdown
for greenhouse gas emissions sources.
Emissions can be reduced by using energy
more efficiently, switching to fuels that
produce less (or no) greenhouse gases, and
capturing the emissions before they enter
the atmosphere.
In general, reducing emissions will
require that existing and planned
transportation, building, and industrial
infrastructure be converted to electricity
that is generated with substantially lower
carbon intensity. Doing so will have
the added co-benefit of reducing the
environmental and human health impacts
associated with coal, oil, and natural
gas extraction and fossil-fuel-generated
electricity (see Challenge 3).109
28â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
Using Energy More Efficiently
High-income countries have already substantially reduced their energy use
per capita and per unit of economic output. These improvements have resulted
from significant technological changes, such as the advent of LED lighting,
energy-efficient appliances, and other efficiency intelligence in buildings;
industrial restructuring to enhance productivity; and investment in fuel-efficient
transportation technologies. Lower- and middle-income countries are beginning
to make similar gains.
Efficiency gains made to date, however, will not be sufficient to avoid a 3.6Â°F
(2Â°C) average rise in global temperatures. More than 80 percent of vehicle
miles traveled in 2050 need to be powered by something other than an internal
combustion engine.110 Substantial efficiencies also are needed in industry and
in the heating and cooling of buildings. In Germany, for example, a high-level
commission calculated that German buildings would need to achieve a 54
percent improvement in efficiency by 2030 to meet stated emission reduction
goals.111 Effectively deploying new and emerging technologies can help advance
these goals. It has been estimated that energy-efficient technologies for residential
and commercial buildings, transportation, and industry that exist today or are
expected to be developed soon could reduce U.S. energy use by 30 percent,
slashing greenhouse gas emissions along with other air pollutants, while also
saving money.112
Curb Climate Change and Adapt to Its Impactsâ |â 29

Prepublication Copy
Switching to Fuels That Produce Less (or No) CO2
As discussed in Challenge 1, there are many sources of energy that produce little or
no CO2 emissions, including solar, wind, geothermal, and hydropower. Although
low-emissions energy sources exist, there is still a long way to go toward their
widespread adoption. As of 2017, U.S. electricity generation was composed of
about 63 percent fossil fuels, 20 percent nuclear, and 17 percent hydropower and
other renewables.113 A study by the Department of Energyâs National Renewable
Energy Laboratory shows that it is feasible for the United States to generate most
of its electricity from renewable energy by 2050, but a number of challenges
remain.114 Cost has been a significant barrier, although costs are dropping for both
solar and wind power technologies.115
Reducing U.S. emissions enough to stay
within the 2.7Â°F (1.5Â°C) limit would
require the current balance of energy
production to shift substantially, such
that 70-85 percent of electricity is
generated from non-carbon-emitting
sources.116 In China, maturation and
economic restructuring of the industrial
sector has already substantially reduced
coal consumption per unit of output, a
trend that is projected to continue and
be further enhanced by their recently
introduced carbon cap and trade
system.117 In addition, China is leading
the charge in developing renewable
energy, for example, building 45 percent
of the worldâs solar installations in
2016.118
Advances are needed to improve the
efficiency and reduce the costs of such energy sources to make them competitive with
traditional fossil fuelâbased sources. In addition, since many renewables produce
energy intermittently, there is a need for energy storage systems with increased capacity,
scalability, reliability, and affordability, as discussed in Challenge 1.
Nuclear power is one low-emission energy source that already comprises one-
fifth of U.S. electricity generation. Increasing the use of nuclear power could
help reduce carbon-emitting energy generation, but there are significant barriers,
including cost, public concerns related to safety and waste disposal, the high
business and regulatory risks involved in designing and building nuclear power
plants, and the lack of progress in developing long-term waste repositories.
Retiring existing nuclear plants will exacerbate the challenge of reducing CO2
emissions from the power system, because large increases in renewable and other
zero-emitting energy sources will be needed simply to replace zero-emitting
nuclear energy. To support continued nuclear capacity, working in combination
with renewables, research is needed on advanced nuclear technologies for next
generation reactors designed to significantly improve performance and safety.119
Moving to electrically powered transportation with increased renewable energy
generation would substantially reduce fossil fuel use, because more than 90 percent
30â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
of the transportation fuels are petroleum based.120 Electric vehicle technology
has advanced substantially in the past 5 years, with roughly 2 million all-electric
and plug-in hybrid vehicles on the road worldwide today,121 and automobile
companies are increasing investments in electric vehicle production. For example,
Volvo announced a plan to transition all of the companyâs car models to electric
or hybrids by 2030, Ford has announced an $11 billion investment in electric
vehicles, and GM plans to release 20 new models of electric vehicles by 2023.122
Several countries, including Britain, France, and Norway, cities such as Beijing, and
several U.S. states have proposed banning gasoline- and diesel-powered cars as
early as 2030.123 Achieving the transition to electric-based transportation systems
raises many engineering challenges beyond the need for low-carbon energy
sources, including the need for charging infrastructure, better battery performance,
and faster recharge times.
Making progress toward reducing emissions will depend in large part on private-
sector investments and on the behavioral and consumer choices of individual
households, which are explored in more detail in Challenge 5. Governments at
federal, state, and local levels can influence those choices through policies and
incentives. Such policies can include setting a price on emissions, such as a carbon
tax or cap-and-trade system; providing information and education on voluntary
emission reductions; and mandates or regulations designed to control emissions,
for example, the Clean Air Act, automobile fuel economy standards, appliance
efficiency standards, building codes, and requirements for renewable or low-carbon
energy sources in electricity generation.
Advancing Climate Intervention Strategies
Even if human-caused carbon dioxide emissions were to cease today, it would
take millennia for natural processes to return Earthâs atmosphere to preindustrial
carbon dioxide concentrations.124 To avoid the worst impacts of warming, it is no
longer enough to reduce emissions. Deploying negative-emission technologies that
remove carbon dioxide from the atmosphere and reliably sequester it will also be
needed.125
Some carbon dioxide removal strategies
focus on accelerating natural processes
that take up carbon dioxide. Changes
in agricultural practices can enhance
soil carbon storage, for example, by
planting fields year-round in crops or
other cover crops.126 Land use and
management practices can be employed
that increase the amount of carbon
stored in terrestrial environments, such
as forests and grasslands and in near-
shore ecosystems, such as mangroves,
tidal marshes, and seagrass beds.127
One recent study estimates that nature-
based approaches can deliver more
than one-third of the carbon reductions
needed by 2030 to stay within the 3.6Â°F
Curb Climate Change and Adapt to Its Impactsâ |â 31

Prepublication Copy
(2Â°C) limit at competitive costs,128 but there are many unknowns. Further research
is needed to determine what conditions and practices can maximize carbon uptake
in plants over the long term. There can also be unintended effects. For example,
planting more trees in northern boreal forests can contribute to warming, because
in winter months the trees can obscure snow that reflects sunlight.
Other technologies being explored seek to actively remove CO2 from the
atmosphere and from point sources and sequester it. One technology involves
growing plants such as switchgrass to be converted to fuel, coupled with capturing
and storing any CO2 emissions from biofuel burning (called bioenergy with carbon
capture and sequestration, or BECCS). Another approach proposes using chemical
processes to capture CO2 directly from the air and concentrate it for storage (called
direct air capture and sequestration, or DACS). These technologies will be needed
around the world because many countries will still be using significant amounts
of fossil-fuel-generated electricity by 2050. They will also be needed to mitigate
emissions where electrification is not possible and for industrial processes that
produce carbon dioxide.
Engineering challenges in carbon removal strategies include the need to reduce
costs, increase the scale of the technologies, and store or reuse the carbon in ways
that keep it from being released back into the atmosphere. Available land is a key
limiting factor for the potential of removing CO2 through reforestation or growing
fuel crops; removing 10 gigatons CO2 per year (about one quarter of global yearly
emissions) by 2050 would require the use of hundreds of millions of hectares of
arable land.129 Land use at that scale could threaten food security, given that food
demands are expected to increase by 25 to 70 percent over the same time period.130
Breakthroughs in agriculture discussed in Challenge 1, including advances in
crop productivity, alternative methods of growing food, food waste reduction, and
changes in diet, will be needed.
A different set of climate intervention strategies seeks to reduce warming by
reflecting sunlight off of specially treated clouds and aerosols. In general, such
technologies are not as developed as carbon dioxide removal strategies and carry
greater risks of unintended consequences that are not well understood.131
Reducing Other Greenhouse Gases
Methane, nitrous oxide, and some industrial gases (e.g., hydrofluorocarbons)
comprise about 18 percent of U.S. greenhouse gas emissions in terms of CO2
equivalents.132 Molecule for molecule, those gases are much stronger climate
warming agents than CO2, although they are less abundant, and some do not last
as long in the atmosphere. Methane, for example, is about 28 times more potent as
a greenhouse gas compared to CO2, making it particularly important to prevent or
capture methane leaks from oil and gas systems, coal mines, shale gas extraction,
and landfills.133 To that end, there is a need for better systems and methodologies to
measure and track methane leakage throughout those systems.134
Agriculture is one of the largest sources of non-CO2 greenhouse gases. Methane is
produced when livestock digest their food and also is emitted in large quantities
from rice paddies. Nitrous oxide arises from the use of nitrogen fertilizers. Precision
agriculture techniques can help farmers minimize fertilizer use and reduce nitrous
oxide emissions (see also Challenge 1). Feeding livestock easier-to-digest foods and
strategically managing livestock wasteâthrough proper storage, reuse as fertilizer,
32â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
and recovery of methaneâalso can help reduce emissions.135 Efforts to curb
agricultural methane emissions can benefit from new insights and biotechnology
tools that offer new ways to study the complex microbial ecosystems involved in
soils, manure management, and livestock digestion.
Some short-lived pollutants that are not greenhouse gases also contribute to
warming. One example is black carbon, commonly called soot, which absorbs
sunlight and traps heat in the atmosphere. Black carbon is produced by incomplete
fuel combustion and burning of biomass (e.g., the dung used in cookstoves). Black
carbon also can amplify regional warming by leaving a heat-absorbing black
coating on otherwise reflective surfaces, such as snow in mountainous regions.
Although North America and western Europe were the major sources of soot
emissions until about the 1950s, low-income nations in the tropics and East Asia
are the major source regions today. Identifying and targeting the largest sources of
black carbon could be crucial to curbing warming in the short term.
What Can Environmental Engineers Do to Curb Climate Change?
Environmental engineers have an opportunity to be leaders in developing
technologies that will help slow warming through alternative energy development,
green infrastructure, carbon capture and sequestration, and monitoring and
measurement, as summarized in Box 2-1. Although the challenge to curb climate
change will stretch environmental engineering beyond its traditional boundaries,
many of the skills typical of environmental engineers can be applicable for
advancing these goals. For example, the design of technologies to capture and
store carbon underground, in soils, and in coastal ecosystems can take advantage
of environmental engineersâ expertise in water chemistry, environmental
microbiology, groundwater and surface water hydrology, and atmospheric
chemistry. Environmental engineers can also bring large-scale perspectives to
illuminate how proposed technologies will interact with multiple systems. Specific
applications of those skills might include
Curb Climate Change and Adapt to Its Impactsâ |â 33

Prepublication Copy
â¢â
Using the tools of geochemistry to engineer accelerated mineralization processes
that would transform carbon into a stable carbonate, while avoiding water
quality impacts.
â¢â
Using the emerging tools of synthetic biology and microbial ecology to abate
greenhouse gas emissions and generate chemicals, materials, and fuels.
â¢â
Using the tools of life-cycle assessment to explore efficiencies for producing low-
carbon liquid fuels from biomass feedstocks without increasing overall water use.
â¢â
Using the tools of life-cycle assessment to assess and optimize the energy
return on investment (the ratio of the amount of usable energy delivered from a
particular energy resource to the amount of energy used to obtain that energy
resource).
BOX 2-1: EXAMPLE ROLES FOR ENVIRONMENTAL ENGINEERS TO HELP CURB
CLIMATE CHANGE
Environmental engineers can play an important role in collaboration with other disciplines to
address four areas related to slowing climate change.
Increasing Energy Efficiency
â¢âsing life-cycle analysis, identify opportunities for improved energy efficiency across sectors
U
to focus energy efficiency improvements toward those with the greatest benefits.
Identify opportunities for the use of the heat that is a by-product of the generation of
â¢â
electricity. Currently much of this heat is âwastedâ during cooling processes.
Advancing Alternative Energy Sources
Identify opportunities for addressing environmental issues associated with promising
â¢â
renewable energy sources, including hydropower, solar, and wind.
D
â¢âevelop low-cost reliable anaerobic carbon conversion systems to turn organic wastes,
including human waste as well as agricultural plant and forest residues, into energy.
D
â¢âevelop strategies to manage nuclear waste.
Advancing Climate Intervention Strategies
D
â¢âevelop biological and mechanical carbon capture methods that can be scaled at reasonable
cost.
D
â¢âevelop uses for captured carbon and methods for safe storage, including monitoring for
leakage.
Improve understanding of the factors that influence the permanence of carbon capture by
â¢â
vegetation and soils.
Reducing Other Greenhouse Gases
â¢âevelop monitoring tools to detect emissions of methane in natural gas systems and methods
D
to minimize or eliminate them.
â¢âevelop technologies and approaches to reduce greenhouse gas emissions from agriculture.
D
Identify the largest sources of black carbon and develop low-cost strategies to reduce these
â¢â
emissions.
34â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
Adapting to Climate Change Impacts
Many of the things people use or do every dayâfrom roads to farms, buildings to
subways, jobs to recreational activitiesâwere optimized for the climate of the 19th
and 20th centuries. They were built with the assumption of certain temperature
ranges, precipitation patterns, frequency of extreme events, and other manifestations
of climate, which are now shifting. Even if humankind were to succeed in limiting
global climate change in accordance with current goals, adaptation will be needed to
protect people, ecosystems, infrastructure, and cultural resources from the impacts of
climate change, many of which are already evident.
Sea level is one area in which those impacts are already being felt. Since 1900,
global mean sea level has risen about 8 inches, driven by expansion of the warming
ocean, melting of mountain glaciers, and losses from the Greenland and Antarctic ice
sheets.136 This rise has caused coastal cities to see an uptick in flooding, both during
storms and as âsunny-dayâ flooding from tides alone. These flooding events disrupt
economies, make it difficult to deliver emergency services, and disproportionately
affect older, infirm, and populations with low socioeconomic status.
Global sea level is expected to rise by an additional 0.5 to 1.2 feet by 2050 and 1
to 4.3 feet by 2100, which will increase the frequency and severity of flooding (see
Figure 2-3). Even at the low end of that estimate, up to 200 million people could
be affected worldwide and 4 million people could be permanently displaced as
frequent or permanent flooding makes low-lying developed areas uninhabitable.137
Some communities already are being forced to relocate as a result of sea-level
rise, including Native American communities in Alaska, communities south of
New Orleans in the Louisiana Delta and island communities in the Pacific and
Indian oceans. In addition to flooding, sea-level rise causes erosion and saltwater
encroachment, which kills forests near the coasts, reshapes marshes and wetlands,
and renders aquifers along the coast unusable for human consumption without
desalination technology.
Curb Climate Change and Adapt to Its Impactsâ |â 35

Prepublication Copy
FIGURE 2-3.â Annual occurrences of tidal flooding, also called sunny-day or nuisance flooding. Recent documented
events are shown in orange and future flooding projections based on three greenhouse gas emission scenarios
known as representative concentration pathways (RCP) ranging from low (RCP2.6) to high (RCP8.5).
Climate change is also expected to intensify regional contrasts in precipitation
that already exist: dry areas are expected to get drier and wet areas to become
even wetter. Changes in precipitation patterns have resulted in heavier rainfalls,
reduced snow cover and glacial extent, and doubled the amount of land area
classified as âvery dry.â138 Warmer temperatures tend to increase evaporation
from oceans, lakes, plants, and soil, exacerbating the impacts in areas of reduced
precipitation.
Extreme precipitation events are becoming more frequent, leading to increased
flooding as well as spikes in the release of some pollutants during heavy storms.139
In August 2016, for example, more than 2 feet of rain fell in central Louisiana over
10 days, an event the National Weather Service called a âone in a thousand yearâ
event. Scientists predict that climate change will cause an increase in the number
of the most severe hurricanes, leading to stronger storm surges and more intense
rainfall events.140 In 2017, Hurricane Harvey dumped a staggering 50 inches of rain
on Houston, which is as much rain as typically falls there over an entire year. Work
is ongoing to assess the future probability of similar rainfall events.
As Earthâs climate warms, changing temperatures are expected to reduce agricultural
productivity for some major crops and may exacerbate the impacts of agricultural
pests and pathogens.141 Extreme heat waves will become more frequent, causing
additional wildfires and further degrading air quality. Urban residents, especially
those without access to air conditioning, are vulnerable to heat waves, as heat island
effects make building and pavement surfaces 7Â°F to 22Â°F (4Â°C to 12Â°C) warmer than
the surrounding natural environment.142
36â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
These changes are expected to pose a number of serious risks to human societies,
affecting freshwater management, ecosystems, biodiversity, agriculture, urban
infrastructure, and human health. To manage the risks and lessen the impacts, there is
an urgent need to develop and deploy adaptation measures. Appropriate adaptation
measures will vary from location to location, and some climate change impacts
will be beyond the scope of adaptation. In some places, incremental steps will be
sufficient to manage risk over the next several decades. In other places, transformative
changes, such as relocation, are likely to be required. Because there is a great
deal of uncertainty regarding future changes, advances in tools that support robust
decision making under deep uncertainty143 and adaptive managementâa model that
maximizes flexibility as new knowledge becomes availableâwill be crucial.
Adaptation strategies range from technological and engineered solutions to social,
economic, and institutional approaches. Social and cultural factors will affect which
strategies are acceptable to local communities. The following examples highlight
current strategies being developed and future areas of focus for adaptation. Other
examples related to water scarcity are discussed in the context of Challenge 1.
Building Disaster Resilience
Communities need to increase their resilience to disasters, such as floods and
wildfires, which are expected to become more frequent and more intense in the Resilience
decades ahead. Flood impacts can be lowered by, for example, developing building is the ability to prepare
and plan for, absorb,
standards based on future flood risks and curtailing development in high-risk areas.
recover from, and more
Improved local projections of flood risk based on changes in climate and land use successfully adapt to
are needed to inform such planning and decision making; advanced GIS technologies adverse events.146
are offering flexible tools that engineers and communities can use toward this goal.
In a departure from past strategies, which emphasized centralized flood control
management with levees and dams that have severe impacts on river and floodplain
ecosystems, communities are increasingly turning to natural systems to manage flood
risks while enhancing habitat, water quality, and other environmental services.
Curb Climate Change and Adapt to Its Impactsâ |â 37

Prepublication Copy
Wildfires play a natural role in preserving the health of forests and other ecosystems
that are adapted to wildfire. However, growth of communities into the wildland-
urban interface and also climate change, which has made fire seasons longer
and droughts worse, has increased the costs and impacts of wildfire144 California
suffered its worst fire season ever in 2017, which was followed by rainstorms that
triggered devastating mudslides. Globally, billions of dollars are spent to remediate
impacts on human health, property damage, loss of tourism, and the restoration of
crucial ecosystem goods and services.145
A major need related to wildfire is the creation of improved models and
measurements to predict wildfire spread and the transport of wildfire smoke
emissions. Other efforts to increase resilience to wildfire include improved
landscape design principles and adaptive management to protect assets through
tree cultivation, prescribed burning, grazing and education programs to reduce
accidental ignitions.
Reducing Impacts on Ecological Systems and Services
For many aquatic and terrestrial species, climate change has altered habitat
conditions, leading to changes in biodiversity and species abundance and
distribution. Increasing ocean temperatures and nutrient inputs from rivers are
expanding the number and size of areas with low-oxygen conditions (âdead
zonesâ), impacting commercial fisheries. Declining Arctic sea ice is reducing
the habitat and hunting ground for polar bears, threatening survival of the
species. Some changes are happening too quickly to allow for adaptation.
However, efforts to reduce other environmental stressors, such as pollution (see
Challenge 3), could reduce the severity of climate impacts and prevent species
extinctions. Other adaptation strategies include habitat restoration, assisted
migration, active management of invasive species, and updated management
strategies for fisheries.147
38â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
Adapting Agricultural Practices
Technological advances during the 20th centuryâs green revolution dramatically
improved agricultural yields, economic stability, and food security in many parts
of the world.148 However, climate change threatens to undercut some of these
advances. Agricultural adaptations such as adjusting planting dates, seed or crop
selection (for example, to develop more flood- and drought-tolerant crops), or
altering irrigation practices have the potential to buffer the impacts of climate
change.149 In the long run, it may be necessary to shift the location of agricultural
operations or even to shift human diets (see Challenge 1). Additional economic and
institutional strategies will be necessary to maintain food security amid increased
weather variability and climate extremes.150
Adapting Infrastructure for Sea-Level Rise
Widespread adaptations in infrastructure are needed to adjust to climate change.
Adaptation strategies include ensuring that critical infrastructure and systems such
as water supply, wastewater, and solid waste management systems, electricity-
generating facilities, hospitals, and transportation systems are resilient to expected
heat, storm, and flooding stressors. With projections of 1 to 4 feet of sea-level rise
by the end of the century,151 engineers are developing ways to hold back the sea
where possible or to buy time until more transformative
adaptation strategies, including managed retreat, are
developed.
BOX 2-2. REBUILDING WETLANDS IN
In the near term, the city of Miami, Florida, is spending LOUISIANA
$400 million to raise streets, build sea walls, and construct The wetlands of southern Louisiana, the
pumps to reduce frequent flooding.152 Natural areas, such largest in the United States, are disappearing
as coastal wetlands and mangroves, are being protected at an alarming rate. More than 1,900 square
or restored to maintain natural buffers against storm surge miles have been lost since 1930 from natural
(see Box 2-2). In the Netherlands, engineers have designed and human causes. Levees and canals have
diverted the flow of sediments from the
Mississippi River that once sustained the
wetlands, while sea-level rise and natural
subsidence continue to affect the coastline.
Coastal wetlands, including salt marshes
and mangroves, provide habitat for local
fisheries and are the first line of protection
against hurricanes and storm surge. Without
action, the state could lose an additional
2,250 square miles of land over the next 50
years. The 2017 Louisiana Coastal Master
Plan,154 approved unanimously by Louisianaâs
legislature, focuses on restoring the natural
flow of sediments to the wetlands, as well
as such projects as marsh creation, barrier
island restoration, and oyster reef restoration.
Wetland loss is problematic in many places,
and environmental engineers can contribute
to the design of green infrastructure that
helps restore lost ecosystems services and
retain habitats at risk from sea level rise.
Curb Climate Change and Adapt to Its Impactsâ |â 39

Prepublication Copy
long-term strategies to protect heavily developed areas and accommodate increased
flooding in less-developed regions. Innovations include smart dikes with embedded
sensors that relay real-time status reports to decision makers and ecologically
enhanced dikes to provide habitat for marine organisms.153
To inform decision making, cities need comprehensive analyses to understand
the adaptation options, their potential impacts, and the benefits and costs of
local, regional, national, and private-sector infrastructure investments to manage
future risks. It will be particularly important to develop economic and institutional
strategies to support low-income and vulnerable communities as these adaptation
measures are implemented.
Anticipating and Responding to Health Threats
Climate change has a broad range of implications for human health.155 Changes in
temperature are expected to increase heat-related illnesses and deaths (see Figure
2-4), while increases in ozone and wildfires are expected to worsen air pollution,
with major effects on human health. Temperature changes may directly affect
the transmission of vectorborne and zoonotic diseases carried by rodents and
insects, such as ticks and mosquitoes, by increasing the frequency and shifting the
geographic areas at risk. Changes in temperature and precipitation patterns may
also affect the prevalence or distribution of foodborne, waterborne, and water-
related diseases.156 Temperature changes can also affect wildlife migration patterns,
potentially leading to more human-wildlife contact and increasing the risk of
infectious diseases that originate in animal populations and spread to humans.
The risk of infectious disease outbreaks also can rise in mass displacement events,
such as natural disasters. In the aftermath of Hurricane Maria in 2017, Puerto Rico
grappled with many health issues including an outbreak of leptospirosis a bacterial
disease.157 Outbreaks in such settings pose enormous challenges for policy makers
and medical, public health, and environmental health personnel, and such events
40â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
can also contribute to food and water insecurity and malnutrition and cause stress
to those who are displaced from their homes.
Adaptation strategies could include strengthening infectious disease surveillance
systems, developing rapid point-of-care diagnostic tests, and improving rapid
response capabilities for disasters and infectious disease outbreaks. Progress toward
ensuring water and food security and reducing air and water pollution would also
reduce the human health impacts from climate change. One strategy for adaptation
in urban areas is to mitigate the urban heat island effect, with efforts needed to test
and evaluate the potential for reflective surfaces, vegetation, and other features to
reduce the temperature of cities.
What Environmental Engineers Can Do to Advance
Climate Change Adaptation
Responding to climate change is about making choices amid substantial
uncertainty. Decision strategies have been developed to support robust planning
and decision making under deep uncertainty.158 To support these decision
processes, engineers and scientists can improve the understanding of potential
long-term climate impacts and examine and communicate the effectiveness and
consequences of adaptation strategies, considering a wide array of environmental,
social, and economic factors (see also Challenge 5). Environmental engineers
are trained with a broad, systems view, which enables them to become a vital
bridge across disciplines and act as integrators of information. Using modeling
and decision support tools, environmental engineers can work with diverse
interdisciplinary teams to synthesize information, analyze adaptation alternatives,
and weigh the costs, benefits, and risks. Environmental engineers have skills in
uncertainty analysis and can support iterative risk management approaches to
analyze climate adaptation strategies for effectiveness and lessons learned in the
context of an evolving understanding of climate science. Examples of specific
opportunities for environmental engineers to help address this challenge are
highlighted in Box 2-3.
42â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
|â

Prepublication Copy
BOX 2-3: EXAMPLE AREAS IN WHICH ENVIRONMENTAL ENGINEERS CAN
ADVANCE EFFORTS TO ADAPT TO CLIMATE CHANGE
Environmental engineers, working with civil engineers and experts in climate science and data,
can play a number of roles in adapting to the expected impacts of climate change:
Building Disaster Resilience
â¢âevelop a national wildfire smoke forecast system.
D
â¢ânalyze changing coastal and inland flood risks under climate change and land-use change,
A
including risks to priority infrastructure.
Adapting Urban and Coastal Infrastructure:
â¢ânalyze the benefits and costs of gray versus green infrastructure, including pollution control
A
and ecosystem services.
Identify cost-effective adaptation strategies for water and wastewater infrastructure at risk
â¢â
from sea-level rise.
Ecosystems:
â¢âevelop a better understanding of ecosystem services in mitigating the impact of climate
D
change.
D
â¢âevelop and evaluate approaches to reduce pollutant loading to ecosystems.
D
â¢âevelop strategies to reduce and mitigate impacts of environmental degradation,
deforestation, and ecosystem loss.
Agriculture:
A
â¢ânalyze large-scale costs and benefits of major changes to agriculture, including location
and dietary changes.
Health:
D
â¢âevelop sensors capable of rapid pathogen detection in humans, animals, and the
environment.
â¢âse green infrastructure, vegetation, and other methods to reduce urban heat island effects
U
while improving water quality in vulnerable communities.
P
â¢âarticipate in formulation and implementation of innovative strategies to reduce the risk of
transmission of vectorborne, zoonotic, foodborne, and waterborne diseases.
Curb Climate Change and Adapt to Its Impactsâ |â 43

Environmental engineers support the well-being of people and the planet in areas where the two intersect. Over the decades the field has improved countless lives through innovative systems for delivering water, treating waste, and preventing and remediating pollution in air, water, and soil. These achievements are a testament to the multidisciplinary, pragmatic, systems-oriented approach that characterizes environmental engineering.

Environmental Engineering for the 21st Century: Addressing Grand Challenges outlines the crucial role for environmental engineers in this period of dramatic growth and change. The report identifies five pressing challenges of the 21st century that environmental engineers are uniquely poised to help advance: sustainably supply food, water, and energy; curb climate change and adapt to its impacts; design a future without pollution and waste; create efficient, healthy, resilient cities; and foster informed decisions and actions.

Welcome to OpenBook!

You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.